Digital printing, including inkjet and laser, is a method of reproducing an image or data onto a medium directly from a computer. Both allow for instant development and fixation of data or an image. Although there are many advantages, there are also some issues with using digital technology, including problems such as poor water resistance (referred to as blotching of the dye), color retention, and yellowing of blank areas. Another key factor in image quality is absorption, or how the liquid ink is incorporated into the solid media, and how it plays a role in the appearance of final data or image. When the ink is applied onto the media, it should stay in a tight, symmetrical dot; otherwise the dots of the ink will begin to feather, or spread out in an irregular fashion to cover a slightly larger area than the digital printer intended. The result is an image or data that appears fuzzy, especially at the edges of objects and text, which is also called wicking. Efforts at improving these potential issues have been made.
EP 1068959A1 discloses cationic polyurethane resin with tertiary amines in the backbone and with said amines quaternized by diethyl sulfate or neutralized with acetic acid. No polyols were used, and resulting polymers were soluble in water and were produced as solvent-containing aqueous solutions with low solids content (20 to 30% wt). FR 2,934,777 relates to polyurethane compositions that can be cationic or can be made cationic. It also relates to cosmetic treatment processes using said polyurethane.
U.S. Pat. No. 6,140,412, discloses aqueous cationic polyurethane solutions for waterproofing ink jet receptive coatings wherein tertiary amino groups in the backbone were neutralized with acetic acid. Only very low molecular weight products were obtained (weight-average molecular weight of less than 8,000 g/mol) in the form diluted (total solids of less than 20% wt.) aqueous solutions containing dimethylformamide solvent.
U.S. Pat. No. 6,358,306 discloses hydrophilic polymers, including polyurethanes, containing tertiary amine groups, including in the side chain, which are not neutralized or quaternized. Because water-soluble polyethylene glycol polyol is used in the synthesis, the demonstration of the invention is limited to polymerization in organic solvents and the final products are polymer solutions in organic solvents. The unique feature of tethered amines for waterborne products was not foreseen and demonstrated.
US 2008090949 directs to the cationic polyurethane dispersions in which tertiary amine group is introduced through a reaction product of diepoxy compound with secondary amine. The limitations of this approach are that the target tertiary nitrogen is removed from the backbone by only one carbon atom and the anchoring atom of the backbone, to which the tether is attached, can only be a carbon and can not be another nitrogen. Additional significant hurdles in implementation of this route are that it requires an extra synthesis step and, in order to obtain maximum dispersability, the most preferred alkyl groups in secondary amine would need to be methyls; this would require handling at elevated temperatures (70° C.) of harmful and highly flammable dimethylamine which has boiling point=7° C. and forms explosive mixtures with air. For this reason, the reduction to practice in US 2008090949 was limited to dibutylamine.